Ramsey County Ag Column

By Bill Hodous

June 1, 2009

Howdy!!!

Good morning to all of you.  I hope this note finds all of you busy in the field and I am quite sure finding a ton of mud.  I checked the NDawn this morning and yesterdays reading had bare soil temperatures reading 62 degrees and turf soil reading 51 degrees.  I would imagine yesterdays warmer day did a great job of heating up the soil surface.  I see there is some earlier corn peaking through and also have found some earlier planted wheat and barley fields emerging.  I have noticed tan spot beginning to be a problem and have included an article published by Marcia McMullen.  Dave Franzen also indicates in this article that nitrogen deficiency might also be part of the problem so a good examination of the crop is in order before determining the problem.

TAN SPOT SHOWING UP IN WINTER WHEAT, SPRING WHEAT MAY SOON FOLLOW
Reports of tan spot in winter wheat this past week have occurred across the state, and recent rains will favor continued development of the fungus, both in winter wheat and spring wheat. The causal fungus, Pyreonphora tritici-repentis, survives in wheat residue, and when conditions are wet and rainy, the fungus’s fruiting bodies on the straw swell and release spores that can infect the leaves. The early infections appear as small tan to brown spots with yellow halos (see figure of symptoms). Dave Franzen, NDSU Extension Soil Fertility specialist, says that “yellow areas in winter wheat may be a combination of tan spot and nitrogen deficiency. Nitrogen deficiency does not automatically cause tan spot, but tan spot is usually more severe when N is deficient. Some growers applied N in the fall, and if these areas are present, this might be an indication that a spring application of N might be better in the future. Fall rains were generally high, and the soils have been very wet this spring. The frost came out of the southeast part of the state the first week in April, so there has been a long time that N has been susceptible for both leaching and denitrification. For this year, these areas could be supplemented with stream-bar 28-0-0 (UAN) before jointing stage to bring them out of deficiency. A rain following application will be needed for greatest efficiency”. To control the tan spot fungus, an early season fungicide may be applied, generally when the crop is in the 4-5 leaf stage. The fungicide often is applied or tank mixed with a herbicide application. A spreader/sticker addition is NOT recommended for the fungicide, if applied in combination with a herbicide. And if soil fertility is an issue, and additional nitrogen needs to be applied, we do NOT recommend applying the early season fungicide in combination with 28-0-0. I cringe when too many things are applied together, and fungicide plus nitrogen may burn the crop. The N application should be a separate operation. A number of fungicides are available for control of early season leaf spot diseases in wheat. These products generally are also registered for barley, if early net blotch or spot blotch should occur. The following table indicates products that have registration in North Dakota for early season use:

Product Active ingredient Early season use rate:

Tilt, Bumper, Propimax, Propiconazole E-AG, Propiconazole 2 fl oz, Stratego Propiconazole + Trifloxystrobin

4-5 fl oz, Quadris Azoxystrobin 6.2 fl oz, Headline Pyraclostrobin 3 fl oz, Quilt Propiconazole + Azoxystrobin

7 fl oz, Penncozeb, Manzate, Dithane  Manex II Mancozeb 1-1/2 lb

All of the products have good activity against leaf spot diseases at the 4-5 leaf stage. The mancozebs are protectants and generally are less rain fast than the other products.  Although early season fungicide use for leaf spot control is fairly common across the state, growers will get the greatest economic response from early season fungicide use under the following conditions:

• susceptible cultivar

• wheat planted into wheat ground

• rainy weather during early leaf stages

Producers who had wheat in a field two years ago may have enough remaining wheat stubble to see some tan spot infection.

524 4th Ave #5, 2nd Floor Ramsey County Courthouse
Devils Lake  ND  58301
701-662-7027
email - NDSU.Ramsey.Extension@ndsu.edu